Numerous studies examining atherosclerotic lesions from human and animal models have[unreadable] established the central role of the macrophage in atherosclerosis. Despite these observations, it is still[unreadable] unclear how the multiple pro- and anti-inflammatory capabilities of the macrophage are balanced within[unreadable] lesions. One potentially important mechanism for them to regulate their function is by the rapid modulation of[unreadable] the repertoire of proteins expressed on their cell surface through proteolytic "shedding". In addition to[unreadable] dynamically altering the cell surface constituents, shedding also leads to the release of soluble ectodomains[unreadable] with distinct biological properties. This proposal will focus on the ADAM family of proteases that have gained[unreadable] recognition as primary effectors of ectodomain shedding.[unreadable] Early lesions of atherosclerosis are characterized by lipid-filled macrophages. Scavenger receptors[unreadable] are responsible for this massive accumulation of cholesterol, and their significance for atherogenesis is[unreadable] highlighted by multiple gene knockout studies. Fas ligand (FasL) is a key cell surface regulator of[unreadable] macrophage apoptosis and activation. Both scavenger receptors and FasL can be proteolytically cleaved[unreadable] from the cell surface resulting in down-regulated cellular expression. The release of soluble scavenger[unreadable] receptor can inhibit foam cell formation in vitro and in vivo, while FasL is proteolytically released in both[unreadable] active and inactive forms. Thus, proteolytic shedding of scavenger receptors and FasL could modulate[unreadable] lesion initiation and progression. However, the enzymes responsible for their shedding have not been fully[unreadable] characterized. In Aim 1, we will determine the proteases involved in the shedding of scavenger receptors[unreadable] and FasL, and the functional significance of shedding on atherogenesis will be examined in Aim 4 by[unreadable] expressing uncleavable mutants of these substrates.[unreadable] In addition to possible effects on lesion initiation, ectodomain shedding may also contribute to lesion[unreadable] progression and plaque rupture. Macrophage activation induces the shedding a multitude of inflammatory[unreadable] mediators, and ADAM17 has been shown to be responsible for the shedding of several of these. In Aim 4,[unreadable] we will test the role of ADAM17 in lesion initiation, progression and plaque rupture by genetically modulating[unreadable] its expression in macrophages. In addition, proteomic approaches will be utilized to identify novel substrates[unreadable] for ADAM17 potentially involved in atherosclerosis (Aim 2), and to determine the role played by oxidants in[unreadable] regulating the activity of this enzyme (Aim 3) in collaboration with Project 4.